It is conventional to provide clearance slots for the tying needles of balers as aforesaid. However, particularly in an underfed baler of the type shown and described in co-pending application Ser. No. 06/611,824, filed May 18, 1984 in the name of Howard Ratzlaff, titled UNDERFED CROP BALER HAVING SINGLE ROTARY FEEDER, and assigned to the assignee of the present invention, such slots may at times become clogged with crop material and impede the needles as they attempt to move through the slots to present twine to the knotter. In severe cases, the wedged-in material may be sufficient not only to bend the needles or deflect them away from the knotter, but also to cause breakage thereof or shearing of a drive bolt associated therewith.